The invention relates to polyurea polymers, particularly polyurea polymers containing hindered amine adducts, and more particularly polyurea polymers containing hindered amine adducts suitable for coatings.
Synthetic polymers have an enormous impact on our day-to-day lives. Polymers have a variety of uses ranging from films and foams to molded plastics and adhesives, just to name a few. One of the most popular uses for polymer compositions is as a coating material. Both one- and two-component coating compositions, particularly polyurethane and polyurea based coating compositions, are known.
One-component coating compositions typically contain fully reacted polyurethanes as the binder. One of the many advantages of one-component coating systems is that they provide good adhesion to a substrate. This adhesive property exists because the one-component systems have relatively long dry times that allow for sufficient wetting of the substrate. While the adhesive properties are advantageous, long dry times, however, may make one-component coatings unsuitable for applications that require rapid dry times, for example pavement marking. Additionally, these coatings require large amounts of solvents to reduce their viscosity. There is a growing concern that solvents, particularly the organic solvents often used in one-component systems, may pose severe environmental and occupational safety hazards. Furthermore, one-component systems suffer from poor wear properties because they do not form highly crosslinked coatings.
Two-component compositions often contain a polyisocyanate component in one container and an isocyanate-reactive component in a second container. One such two-component system is a polyurea system. An exemplary polyurea system is disclosed in U.S. Pat. No. 5,218,005 to Zimmerman et al. Zimmerman et al. propose a polyurea system containing polyisocyanate, polyoxyalkylene polyamine, and polyamine adduct. U.S. Pat. No. 5,516,873 to Hicks et al. describes a polyurea system containing polyisocyanate, aldimine, and a compound containing an aspartate group. U.S. Pat. No. 5,559,204 to Squiller et al. discusses a polyurea coating system containing an aldimine/aspartate as the isocyanate-reactive component. U.S. Pat. No. 5,616,677 to Primeaux, II et al. proposes an aliphatic spray polyurea elastomer containing an aliphatic isocyanate, an amine-terminated polyoxyalkylene polyol, and a cycloaliphatic diamine chain extender.
Polyurea systems may provide highly crosslinked coatings that do not require large amounts of solvents. Extensive crosslinking may give these coatings excellent physical properties, including elongation and abrasion resistance. Additionally, the two components may react very quickly, with typical gel and dry times measured in seconds. Such rapid dry times appear to make these coatings suitable for applications like pavement marking. However, the reaction between the two components may actually occur too quickly. Due to the very rapid cure speed, polyurea systems must be applied with specialized application equipment, in which the two components are mixed immediately prior to the application. Even with the specialized equipment, the acceptance of polyurea systems has been low due to the application difficulties and performance problems. For instance, in coating applications polyureas have been reported to cure before the substrate is adequately wetted, yielding a film with poor adhesion.
It is therefore an object of the present invention to provide improved polymeric compositions that combine the exceptional properties of two-component polyurea systems, including rapid cure rate, with the excellent adhesive properties of one-component polyurethane systems.
It is another object of the present invention to provide an isocyanate-reactive component for use in such improved polymeric systems.
It is yet another object of the present invention to provide methods of forming such improved polymeric systems.
It is still another object of the present invention to provide methods of applying such improved polymeric systems to a substrate.
These and other objects, features and advantages are achieved by the various compositions and methods of the present invention. In one embodiment, a polymeric composition includes an isocyanate component and an amine component, which includes: 
where R1 represents a hydrocarbon radical, X represents an organic group, and a is an integer.
In another embodiment, a polymeric composition may include from about 5 to about 50 weight percent of an isocyanate component, and from about 50 to about 95 weight percent of an amine component including: 
where R1 represents a hydrocarbon radical, X represents an organic group, and a is an integer.
In yet another embodiment, an amine composition may include from about 30 to about 100 weight percent of a compound of Formula I, 
and from about 0 to about 70 weight percent of a compound of Formula II, 
where R1 and R2 represent hydrocarbon radicals, X and Y represent organic groups, and a and b are both integers.
In further embodiments, methods of forming compositions of the present invention and of applying polymeric compositions of the present invention to substrates are provided.
By utilizing at least one hindered amine adduct as the amine component, polymeric compositions of the present invention combine the exceptional properties of a two-component polyurea system, including rapid cure time, with the excellent adhesive qualities of a one-component polyurethane system.
The invention will now be described in greater detail with reference to the preferred embodiments which follow. It should be appreciated, however, that these embodiments are for illustrative purposes only, and are not meant to limit the invention as defined by the claims.
Polymeric compositions of the present invention may be formed by reacting an isocyanate component with an amine component. The isocyanate component used in the polymeric composition may be selected from isocyanates known in the art of polyurethane and polyurea chemistry including any of the aliphatic, cycloaliphatic, araliphatic or aromatic polyisocyanates. Examples of particularly suitable polyisocyanates include monomeric isocyanates, isocyanate functional prepolymers, isocyanate functional adducts, and mixtures thereof.
Examples of suitable monomeric isocyanates include 1,6 hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, isophorone diisocyanate, bis-(4-isocyanatocyclohexyl)-methane, 2,4-diphenyl-methane diisocyanate, 4,4xe2x80x2-diphenyl-methane diisocyanate, 1,1xe2x80x2-methylenebis(4-isocyantocyclohexane), trimethyl-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,4xe2x80x2-dicyclohexyl-methane diisocyanate, bis-(4-isocyanato-3-methylcyclohexyl)-methane, 1,3-bis-(isocyanatomethyl)-cyclohexane, 1,4bis-(isocyanatomethyl)-cyclohexane, xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetramethyl-3-xylylenediisocyanate, xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetramethyl-1,4-xylylenediisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, 2,4-hexahydrotoluylene diisocyanate, 2,6-hexahydrotoluylene diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, and 1,5-diisocyanato naphthalene and mixtures thereof.
The isocyanate component may also be a monomeric isocyanate material that is chain extended by an alcohol to form an isocyanate functional prepolymer. Examples of suitable functional prepolymers can be prepared by reacting a monomeric isocyanate with a low molecular weight alcohol, to form for example prepolymers based on isophorone diisocyanate and trimethylol propane, prepolymers of isophorone diisocyanate and pentaerythritol, and prepolymers of isophorone diisocyanate and hexane diol. The alcohol may include, but is not limited to, diols, triols, and tetraols known to one skilled in the art. Examples of suitable alcohols include, but are not limited to, trimethylol ethane, trimethylol propane, glycerine, pentaerythritol, ethoxylated pentaerythritol, propoxylated pentaerythritol, ethylene glycol, diethylene glycol, and neopentyl glycol. The alcohol may also be in the form of low molecular weight hydroxyl functional acrylic resins, polyesters, or polyethers such as, but not limited to, polypropylene glycol and polyethylene glycol or a combination thereof.
Examples of suitable isocyanate functional adducts include polyisocyanates which contain isocyanurate groups, uretdione groups, biuret groups, allophanate groups, carbodiimide groups, or oxadiazinetrione groups, such as biuret of isophorone diisocyanate, isocyanurate trimer of isophorone diisocyanate, biuret of hexamethylene diisocyanate, and isocyanurate trimer of hexamethylene diisocycanate.
The most preferred polyisocyanate is the isocyanurate of 1,6 hexamethylene diisocyanate, having an NCO content by weight of preferably from about 10 to about 35%, more preferably from about 15 to about 30%, and most preferably from about 20 to about 25%.
The polymeric composition preferably comprises from about 5 to about 50 weight percent of the isocyanate component, and more preferably between about 25 to about 50 weight percent. These percentages are based on the weight of the reactive components.
The amine component typically comprises hindered amine adducts, represented by Formula I: 
wherein
R1 is a hydrocarbon radical that may be represented by an alkyl group, an aryl-alkyl group, a hydroxy-alkyl group or an alkoxy-alkyl group. Exemplary hydrocarbons include t-butyl, t-octyl, C12-C14 and C16-C22 alkyls cyclohexane; X is an organic group having a valence of a. X may be propyl, ethyl, ethanol, methyl, methynol, 2-ethyl hexyl, lavryl hexane, tripropyl hexane, cyclohexane, isobornyl and the like, and is preferably propyl, methyl, methanol or isobornyl; and a represents integers having a value in the range of 1 to 20, more preferably 1 to 15, and most preferably 1 to 10. Hindered amine adducts of Formula I may be prepared by reacting a primary amine with an acrylate.
The primary amine may have the formula Rxe2x80x94NH2, where R is a hydrocarbon radical that may be represented by an alkyl group, an aryl-alkyl group, a hydroxy-alkyl group, or an alkoxy-alkyl group. Examples of suitable primary amines include butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine and polyoxypropylene amine. R is preferably a tertiary alkyl group containing from about 4 to about 30 carbon atoms, such as t-butyl or t-octyl. Examples of preferable tertiary alkyl primary amines include, but are not limited to, tertiary-butyl primary amine, tertiary-octyl primary amine, 1-methyl-1-amino-cyclohexane, tertiary-tetradecyl primary amine, tertiary-hexadecyl primary amine, tertiary-octadecyl primary amine, tertiary-octacosanyl primary amine, and other primary amines containing higher tertiary C8 to C30 alkyl groups. Mixtures of tertiary alkyl primary amines may also be used. A suitable class of amines are commercially available under the Primene(copyright) tradename from Rohm and Haas Company of Philadelphia, Pa. Tertiary alkyl primary amines and methods for their preparation are known to those of ordinary skill in the art.
Suitable acrylates include those having the formula: 
wherein X and a are as defined above. Suitable acrylate oligomers for preparing the hindered amine adducts of Formula I include tripropylene glycol diacrylate, trimethylolpropane triacrylate, isobornyl acrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, hexanediol diacrylate, cyclohexane-dimethanol diacrylate, tetraethylene glycol diacrylate, diacrylate of bisphenol A based epoxy, triacrylate of glycerol, ethoxylated trimethylolpropane triacrylate, acrylate of epoxidized soya oil, and urethane acrylates based on isophorone diisocyanate and petaerythritol triacrylate.
The amine component may also comprise hindered amine adducts, represented by Formula II: 
wherein R2 is a hydrocarbon radical that may be represented by an alkyl group, an aryl-alkyl group, a hydroxy-alkyl group or an alkoxy-alkyl group. Exemplary hydrocarbons include t-butyl, t-octyl, C12 and C14 and C16-C22 alkyls and cyclohexane; Y represents an organic group having a valence b and represents the hydrocarbon group obtained by removal of the glycidyl ether groups from epoxide resins based on bisphenol A, bisphenol F, tetrabromobisphenol A, phenol-formaldehyde condensates, hydrogenated bisphenol A, resocinol, sorbitol, etc. Preferably, Y represents the hydrocarbon group obtained by removal of the glycidyl ether groups from epoxide resins based on bidphenol A or bisphenol F; and b represents integers having a value in the range of 1 to 10, more preferably 1 to 8, and most preferably 1 to 6. Hindered amine adducts of Formula II may be prepared by reacting a primary amine with an epoxide or glycidyl ether.
The primary amine may be selected from the group described above, with tertiary alkyl primary amines preferable. Suitable epoxides or glycidyl ethers include those having the formula: 
wherein Y and b are as described above. Suitable epoxide resins for preparing the hindered amine adducts are ones based on bisphenol A and bisphenol-F, such as, but not limited to, the diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol-F, diglycidyl ether of tetrabromobisphenol A, epoxy novolacs based on phenol-formaldehyde condensates, epoxy novolacs based on phenol-cresol condensates, epoxy novolacs based on phenol-dicyclopentadiene condensates, diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of resorcinol, tetraglycidyl ether of sorbitol, tetra glycidyl ether of methylene dianiline or mixtures thereof; and glycidyl ethers of the following alcohols: 2-ethylhexanol, alcohols containing from 8 to 14 carbon atoms, cresol, p-tertiary butyl phenol, nonyl phenol, phenol, neopentyl glycol, 1,4-butanediol, cyclohexane dimethanol, propylene glycol, dibromo neopentyl glycol, trimethylol propane, trimethylol ethane, and n-butanol. Preferably, the epoxide has an average epoxide equivalent weight (EEW) of from about 120 to about 2000, and more preferably from about 140 to about 1000.
The amine component preferably comprises from 0 to about 100 weight percent of the hindered amine adduct represented by Formula I. The amine component more preferably comprises from about 30 to about 100 weight percent of the hindered amine adduct represented by Formula I and from about 0 to about 70 weight percent of the hindered amine adduct represented by Formula II.
The hindered amine adducts of Formulas I and II may be prepared in accordance with procedures that are known in the art. Typically, the amine adduct is formed by reacting an amine with the amine-reactive component. These reactions can be carried out in suitable reaction vessels at temperatures ranging from about 40 to 150xc2x0 C. Preferably, a nitrogen or other inert gas cover may be used to exclude oxygen from the reaction. Where the amine component comprises hindered amine adducts represented in Formulas I and II, the adducts may be prepared separately and mixed after the individual synthesis of each adduct, or more conveniently, the hindered amine adducts can be prepared in a single reaction vessel either simultaneously or in sequence.
The polymeric composition preferably comprises from about 50 to about 95 weight percent of the amine component, and more preferably between about 50 to about 75 weight percent. These percentages are based on the weight of the reactive components.
Compositions of the present invention may also encompass other components that are conventionally employed in polymerizable systems. These components include, but are not limited to, accelerators, promoters, plasticizers, pigments, colorants, dyes, surfactants, thickeners, heat stabilizers, leveling agents, anti-cratering agents, fillers, sedimentation inhibitors, ultraviolet-light absorbers, and the like. Additives such as promoters, heat stabilizers, ultraviolet-light absorbers, etc. may be intimately dispersed in the reaction mixture and apparently thereby become an integral part of the polymer.
The polymeric composition of the invention may be utilized in conjunction with a paint composition, although other uses are contemplated within the scope of the invention. The paint composition may employ those components, additives, and the like which are known to the skilled artisan. Examples of materials that are typically employed in traffic paint compositions are set forth in U.S. Pat. No. 4,105,808 to McKenzie, the disclosure of which is incorporated herein by reference in its entirety. In particular, the paint composition comprises pigments such that the paint is visible after being applied to the pavement. Typically, white or yellow pigment is employed in the composition, preferably in an amount ranging from about 15 to about 25 parts based on the weight of the composition.